Advanced aircraft and aerospace systems demand lighter weight structures which depend upon the availability and effective utilization of superior structural materials. The material requirements are not only for superior mechanical properties; the materials must also possess a high degree of thermal oxidative stability.
In U.S. Pat. No. 3,671,542, there is disclosed a series of new organic fibers which exhibit exceptionally high strength and modulus. The modulus values of the fibers approach those of boron and graphite while their tenacity values surpass those of any known fibers. The unique fibers are derived from the wet spinning of optically anistropic liquid crystal aromatic polyamide dopes. The anistropic solutions are obtained from the group of polyamides whose chain-extending bonds from each aromatic nucleus are essentially coaxial or parallel and oppositely directed in liquid media. As disclosed in the aforementioned patent, strong acids are used as solvents, which is a disadvantage from a processing standpoint. And while the aromatic polyamides exhibit superior mechanical properties, they do not meet the thermal and hydrolytic stability requirements for all aircraft and aerospace systems.
It is a principal object of the present invention, therefore, to provide polymer systems which exhibit the desired superior physical properties as well as the required high degree of thermal oxidative and hydrolytic stability.
Another object of the invention is to provide rod-like, para-ordered aromatic heterocyclic polymers with improved thermal oxidative stability as well as improved solubility characteristics.
A further object of the invention is to provide a method for synthesizing the polymers.
Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.